Problem A. 649. (September 2015)
A. 649. A convex polyhedron has only quadrilateral faces. Show that it is possible to split every face into two triangles by drawing one of its diagonals in such a way that at each vertex of the polyhedron, an even number of triangles meet.
Proposed by: János Nagy, Budapest
Deadline expired on October 12, 2015.
5 students sent a solution. 5 points: Bodnár Levente, Lajkó Kálmán. 1 point: 1 student. 0 point: 2 students.